vl: Allow multiple -overcommit commands

vl: Allow multiple -overcommit commands

Both cpu-pm and mem-lock are related to system resource overcommit, but
they are separate from each other, in terms of how they are realized,
and of course, they are applied to different system resources.

It's tempting to use separate command lines to specify their behavior.
e.g., in the following example, the cpu-pm command is quietly
overwritten, and it's not easy to notice it without careful inspection.

  --overcommit mem-lock=on
  --overcommit cpu-pm=on

Fixes: c8c9dc42b7ca ("Remove the deprecated -realtime option")
Suggested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>